The present invention relates to a transfer tape which is suitable for transferring an adhesive to an extremely small item such as a semiconductor chip or to portions of an extremely small area such as sites of a lead frame predetermined for mounting IC chips.
When securing an extremely small electronic component such as a semiconductor chip onto a substrate such as a circuit board or a lead frame, it is common practice to employ the method known as the xe2x80x9cdispenser methodxe2x80x9d or the method of using a film adhesive.
The dispenser method, a given amount of liquid adhesive is applied to sites of a substrate which are predetermined for securing semiconductor chips with the use of a dispenser, followed by the compression bonding/fixing of semiconductor chips thereonto. However, this dispenser method has drawbacks in that controlling the amount of adhesive discharged is difficult, thereby causing the adhesive amount to be uneven, bringing about a variation of quality, and in that a bleeding phenomenon occurs in the curing of the liquid adhesive.
In the method of using a film adhesive, a film adhesive cut into substantially the same shape as that of the chip is stuck to sites of a substrate predetermined for securing semiconductor chips in advance, or a film adhesive cut into substantially the same shape as that of the chip is stuck to chips, and the chips are secured through the film adhesive to the substrate. However, in this method, it is required to cut the film adhesive into substantially the same shape as that of the chip in advance, so that the method is time-consuming and, when a wide variety of chips are employed, timely preparations cannot be effected. Further, the work for sticking the film adhesive of the same extremely small size as that of the chip is requisite, so that the method is very laborious.
The present invention overcomes the above-described shortcomings encountered in the prior art and provides a transfer tape which enables transferring a given amount of adhesive to an extremely small item such as a semiconductor chip or to portions of an extremely small area such as sites of a lead frame predetermined for mounting IC chips by simple operation.
The transfer tape of the present invention comprises a base material and, superimposed thereon with intervals, an adhesive.
The terminology xe2x80x9cwith intervalsxe2x80x9d used herein preferably means that the adhesive is in the form of a pattern of independent constituents whose respective areas are substantially equal to each other, the area per pattern constituent being in the range of 0.01 to 10% of the area of the underside of an object onto which the adhesive is transferred, and having an average shortest distance between pattern constituents in the range of 0.5 to 10% of a maximum length of the object""s underside.
The first method of securing semiconductor chips according to the present invention comprises:
sticking semiconductor chips to be secured at their backs to the above transfer tape,
peeling the semiconductor chips from the transfer tape in such a manner that the adhesive is transferred onto the backs of the semiconductor chips, and
securing the semiconductor chips through the adhesive onto a substrate.
The second method of securing semiconductor chips according to the present invention comprises:
sticking the above transfer tape to sites of a substrate which have been predetermined for securing semiconductor chips,
peeling the base material of the transfer tape in such a manner that the adhesive is transferred onto the substrate sites predetermined for securing semiconductor chips, and
securing semiconductor chips through the adhesive onto the substrate.